Alan F. HamletPhilip Mote

Dennis P. Lettenmaier

JISAO Center for Science in the Earth System Climate Impacts Group

and Department of Civil and Environmental EngineeringUniversity of Washington

October, 2003

Considering Climate Variability and Climate Change in Long-Term Water

Planning

http://www.hydro.washington.edu/Lettenmaier/Presentations/2003/hamlet_fish_hydro_oct_2003.ppt

Example of a flawed water planning study:The Colorado River Compact of 1922

The Colorado River Compact of 1922 divided the use of waters of the Colorado River System between the Upper and Lower Colorado River Basin. It apportioned **in perpetuity** to the Upper and Lower Basin, respectively, the beneficial consumptive use of 7.5 million acre feet (maf) of water per annum. It also provided that the Upper Basin will not cause the flow of the river at Lee Ferry to be depleted below an aggregate of 7.5 maf for any period of ten consecutive years. The Mexican Treaty of 1944 allotted to Mexico a guaranteed annual quantity of 1.5 maf. **These amounts, when combined, exceed the river's long-term average annual flow**.

      

Despite a general awareness of these issues in the water planning community, there is growing evidence that future climate variability will not look like the past and that current planning activities, which frequently use a limited observed streamflow record to represent climate variability, are in danger of repeating the same kind of mistakes made more than 80 years ago in forging the Colorado River Compact.

Long-term planning and specific agreements influenced by this planning (such as the long-term licensing of hydropower projects) should be informed by the best and most complete climate information available, but frequently they are not.

What’s the Problem?

Overview:

•What do we know about Pacific Northwest climate variability and river flow over the past 250 years or so?

•What should we expect for the 21st century?

•How can planners bring this information to bear on long-range water planning?

Hydroclimatology of the Pacific Northwest

Annual PNW Precipitation (mm)

Elevation (m)

The Dalles

WinterPrecipitation

SummerPrecipitation

(mm)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

10 11 12 1 2 3 4 5 6 7 8 9

Month

Nor

mal

ized

Stre

amflo

w

SnowDominated

Transient Snow

Rain Dominated

Hydrologic Characteristics of PNW Rivers

Temperature warms,precipitation unaltered:

•Streamflow timing is altered• Annual volume stays about the same

Precipitation increases,temperature unaltered:

•Streamflow timing stays about the same•Annual volume is altered

Sensitivity of Snowmelt and Transient Riversto Changes in Temperature and Precipitation

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1973

1973

1973

1973

1973

1973

1974

1974

1974

1974

1974

1974

Water Year

Flow

(cfs

)

0

100000

200000

300000

400000

500000

600000

700000

800000

900000

1973

1973

1973

1973

1973

1973

1974

1974

1974

1974

1974

1974

Water Year

Flow

(cfs

)

A history of the PDOwarm

coolwarm

A history of ENSO

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Pacific Decadal Oscillation El Niño Southern Oscillation

150000

200000

250000

300000

350000

400000

450000

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

2000

Apr-S

ept F

low

(cfs

)

Effects of the PDO and ENSO on Columbia River Summer Streamflows

Cool CoolWarm Warm

high highlow low

Ocean Productivity

PDO

Long-Term Trends in Temperature, Precipitation, and Streamflow

Area-weighted Regional Avg=1.5 F/century

Annual Precipitation TrendsFrom HCN stations

Winter precipitation and annual flow in the Columbia River are highly correlated and are both gradually increasing since 1916

y = 146.69x + 192462

0

50000

100000

150000

200000

250000

300000

35000019

16

1921

1926

1931

1936

1941

1946

1951

1956

1961

1966

1971

1976

1981

1986

1991

1996

regressedobs wy flowLinear (obs wy flow)

(Trend ~ +7% per century)

(Comparison of Annual Flow at The Dalles and Predicted Flow Based on Oct-Mar Basin-Average Precipitation from 1916-1997)

Trends in Annual Streamflow at The Dalles from 1858-1998 are strongly downward.

0

50000

100000

150000

200000

250000

300000

350000

1858

1868

1878

1888

1898

1908

1918

1928

1938

1948

1958

1968

1978

1988

1998

Ann

ual M

ean

Flow

(cfs

)

Annual

5 yr mean

10 yr mean

Linear (Annual)

1750 1775 1800 1825 1850 1875 1900 1925 1950 1975 2000Year

5.0

5.1

5.2

5.3

5.4

5.5

Log1

0 m

ean

flow

, The

Dal

les,

OR

(cfs

)

Source: Gedalof, Z., D.L. Peterson and Nathan J. Mantua. (in review). Columbia River Flow and Drought Since 1750. Submitted to Journal of the American

Water Resources Association.

The Dust Bowl was probably not the worst drought sequence in the past 250 years

red = observed, blue = reconstructed

Global Climate Change Scenarios and Impacts on the PNW

Humans are altering

atmospheric composition

The earth is warming -- abruptly

Natural Climate Influence Human Climate Influence

All Climate Influences

Natural AND human influences explain the observations best.

Emissionsscenarios we choseare “middle of the road”ones

1 BMRC2 CCC3 CCSR4 CSIRO5 ECHAM36 ECHAM47 GFDL8 HadCM29 IAP10 MRI11 CERFACS12 PCM13 GISS14 HadCM315 LMD16 CSM

Higher Predictive SkillFor Temperature

Lower Predictive SkillFor Precipitation

Climate models predict temperature more accurately than precipitation.

Precipitation Fraction, 2020s

0.5

0.75

1

1.25

1.5

1.75

J F M A M J J A S O N D

Frac

tion

hadCM2

hadCM3

PCM3

ECHAM4

mean

Delta T, 2020s

-1

0

1

2

3

4

5

J F M A M J J A S O N D

Degr

ees

C

hadCM2

hadCM3PCM3ECHAM4mean

Delta T, 2040s

-1

0

1

2

3

4

5

J F M A M J J A S O N D

Degr

ees

C

hadCM2

hadCM3

PCM3

ECHAM4

mean

Precipitation Fraction, 2040s

0.5

0.75

1

1.25

1.5

1.75

J F M A M J J A S O N D

Frac

tion

hadCM2

hadCM3

PCM3

ECHAM4

mean

Four Delta Method Climate Change Scenarios for the PNW

~ + 1.7 C ~ + 2.5 C

Somewhat wetter winters and perhaps somewhat dryer summers

ColSimReservoir

Model

VICHydrology Model

Changes in Mean Temperature and

Precipitation or Bias Corrected Output

from GCMs

Current Climate 2020s 2040s

Snow Water Equivalent (mm)

VIC Simulations of April 1 Average Snow Water Equivalentfor Composite Scenarios (average of four GCM scenarios)

The main impact: less snow

Reductions in Snowpack for PCM Scenarios(low sensitivity)

Regulated Flow

Historic Naturalized Flow

Estimated Range of Naturalized FlowWith 2040’s Warming

Naturalized Flow for Historic and Global Warming ScenariosCompared to Effects of Regulation at 1990 Level Development

0

1000

20003000

4000

5000

60007000

8000

900010

/110

/29

11/2

612

/24

1/21

2/18

3/18

4/15

5/13

6/10 7/8

8/5

9/2

Date

Inflo

w (a

cre-

ft) Simulated 20thCentury Climate2020s ClimateChange Scenario2040s ClimateChange Scenario

Effects to the Cedar River (Seattle Water Supply)for “Middle-of-the-Road” Scenarios

Frequency of Drought in the Columbia River Comparable to Water Year 1992

(data from 1962-1997)

0

2

4

6

8

10

12

14

16

Base Mean2020s

Mean2040s

ECHAM42040s

PCM2040s

Scenario

Num

ber o

f Occ

uren

ces

x 2

x 4.7

x 1.3 x 1.3

Source: Payne, J.T., A.W. Wood, A.F. Hamlet, R.N. Palmer and D.P. Lettenmaier, 2004, Mitigating the effects of climate change on the water resources of the Columbia River basin, Climatic Change (in

press).

Adaptation to climate change will require complex tradeoffs between ecosystem protection and hydropower operations

2070-2098

60

80

100

120

140

FirmHydropower

Annual FlowDeficit atMcNary

Perc

ent o

f Con

trol

Run

Clim

ate

PCM Control Climate andCurrent Operations

PCM Projected Climateand Current Operations

PCM Projected Climatewith AdaptiveManagement

Monitoring Climate Change Impacts

20th century decline in NH snow cover

R.D. Brown, J. Climate, 2000

Satellite meas.

Surface measurements

Trends in April 1 snow water equivalent, 1950-2000Mote, P.W., 2003: Trends in snow water equivalent in the Pacific

Northwest and their climatic causes. Geophysical Research Letters.

Snowmelt runoff timing trends, 1948-2000

Graphic provided by Dan Cayan, Scripps Institute of Oceanography and the USGS. To appear in Climatic Change, 2003

Strategies and Tools for Incorporating Climate Information in

Long-Term Water Planning

Broad Strategies for Incorporating Climate Variability and Climate Change in Long-Term Water Planning

Identify and Assess Climate LinkagesIdentify potential linkages between climate and resource management that could affect outcomes in the long term. What’s being left out? Are there future “deal breakers” in these omissions? (e.g. ocean productivity, glaciers maintaining summer streamflow in the short term)

Design for Robustness and SustainabilityUse modeling studies to test preferred management alternatives for robustness in the face of climate variability represented by paleoclimatic studies, conventional observations, and future climate change projections.

Identify Limits and Increase Response CapabilityUse estimates of uncertainties or “what if” scenarios to find the performance limits inherent in preferred management alternatives. How can response capability be increased?

Expect Surprises and Design for Flexibility to Changing ConditionsDesign contingency planning into management guidelines to allow for ongoing adaptation to unexpected (or uncertain) conditions without recursive policy intervention.

Observed Streamflows

Planning Models

System Drivers

Critical Period Planning Methods for Water Studies

Columbia River at The Dalles

0100000200000300000400000500000600000700000800000

1925

1925

1925

1926

1926

1927

1927

1927

1928

1928

1929

1929

1930

1930

1930

1931

1931

1932

1932

1932

1933

1933

1934

1934

Observed Streamflows

Climate Change Scenarios

Planning Models

Long term planning for climate change may include a stronger emphasis on drought contingency planning, testing of preferred planning alternatives for robustness under various climate change scenarios, and increased flexibility and adaptation to climate and streamflow uncertainty.

Altered Streamflows

System Drivers

Incorporating Climate Change in Critical Period Planning

Bias Corrected Time Series Plot for the Current Climate

Bias Corrected Time Series Plot for the Composite 2040 Scenario

Web-Based Data Archive

http://www.ce.washington.edu/~hamleaf/climate_change_streamflows/CR_cc.htm

Conclusions:

The integrated and cumulative impacts of climate variability and climate change on water resources need to be incorporated more effectively in long-term water planning if we are to avoid costly mistakes in forging long-term water and energy policies and in allocating water for future use.

Including better information on climate variability and climate change in water planning will require some changes in the way we do things, but good tools and sources of information are available to assist with the process.